Problem

Synthetic backups may unexpectedly fail to be scheduled. This can lead to data loss if older full backups expire and no newer synthetic backups have been taken. (Updated December 1, 2009)

Solution

Introduction:Due to a scheduling issue in the
NetBackup Policy Execution Manager (nbpem), synthetic full backups may
fail to be scheduled and are skipped. Other schedules ("traditional" full
and incremental) will continue to run, but new synthetic full backups are never
scheduled and continue being skipped until a traditional full backup is run
followed by an incremental backup. This may correct itself with normal
scheduling, subject to the policy schedule configuration, or by manual
intervention from the administrator by running a full backup.

If the
traditional full backups in a synthetic backup policy are set with a retention
value shorter than the time between full backups, a data loss condition (gap)
will be experienced when the expected synthetic full backup is unavailable for
restore.

What is Affected:The following versions of NetBackup
may be affected if synthetic policies are enabled:

NetBackup
6.5.3 through 6.5.4

How to Determine if
Affected:Synthetic backup attempts which are expected to have run do not
appear in the Activity Monitor.

If all full backups from a given policy
should expire, incremental backups running as fulls may be seen in the Activity
Monitor. These would appear as incremental backups, but with an elapsed
time and size comparable to a full backup.

Output from the following
nbpemreq command can reveal this
condition:# nbpemreq -subsystems screen
1

nbpemreq can be found at the following
paths:

For UNIX/Linux:/usr/openv/netbackup/bin/admincmd

For Windows:<install_path>\VERITAS\NetBackup\bin\admincmd

The output
will show that the synthetic schedule is not scheduled for a future run due to
"no incrementals found:"07/16/09 07:55:48.595
[nbpemreq ] Weekly_Synth::1: Ignored, no incrementals for synthetic

Note: In the examples above,
Weekly_Synth and Daily_Incr are schedule names for the synthetic
full and incremental schedules. The number following the schedule name is
the stream number - multistreamed policies will have similar output for every
stream for each schedule in the policy and an entry for the parent job with a
"stream number" of -1.

In addition, running an nbpemreq
-predict_all command may fail to return a prediction for the next run using
the synthetic schedule of the policy.

Formal Resolution:The
formal resolution to this issue (Etrack 1728027) is included in the
following release:

Workaround:Increasing the retention value of traditional full
backups ensures that data remains available for restore, even if synthetic full
backups are not available.

If applying the NetBackup 6.5.5 release update
is not feasible at this time, a fix for this issue has been posted for NetBackup
6.5.4. To obtain a replacement nbpem binary, click on the link
below (or in the "Related Documents" section) to obtain TechFile
331593:http://support.veritas.com/docs/331593

If this issue is experienced and both applying the 6.5.5 release update
AND the above workarounds are not feasible, please contact Symantec technical
support, referencing this TechNote ID and Etrack 1728017 to obtain a
replacement nbpem binary for NetBackup 6.5.3 or 6.5.3.1.

Best
Practices:Symantec strongly recommends the following best
practices:1. Always perform a full backup prior to and after any changes to
your environment.2. Always make sure that your environment is running the
latest version and patch level.3. Perform periodic "test" restores.4.
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Please note that this document is a translation from English, and may have been machine-translated. It is possible that updates have been made to the original version after this document was translated and published. Veritas does not guarantee the accuracy regarding the completeness of the translation. You may also refer to the English Version of this knowledge base article for up-to-date information.

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